The stiffness of a body is a measure of the resistance offered by an elastic body to deformation. A body have a rotational stiffness when it is in a ... more
In probability theory and statistics, skewness is a measure of the asymmetry of the probability distribution of a real-valued random variable about its ... more
In probability theory and statistics, kurtosis is any measure of the “tailedness” of the probability distribution of a real-valued random ... more
Calculates the logarithmic mean size (moments method) of the particles’ size distribution of a soil, in phi scale... more
(a) The figure shows the forearm of a person holding a book. The biceps exert a force FB to support the weight of the forearm and the book. The triceps are assumed to be relaxed. (b) Here, you can view an approximately equivalent mechanical system with the pivot at the elbow joint
There are four forces acting on the forearm and its load (the system of interest). The magnitude of the force of the biceps is FB, that of the elbow joint is FE, that of the weights of the forearm is wa , and its load is wb. Two of these are unknown FB, so that the first condition for equilibrium cannot by itself yield FB . But if we use the second condition and choose the pivot to be at the elbow, then the torque due to FE is zero, and the only unknown becomes FB .
The torques created by the weights are clockwise relative to the pivot, while the torque created by the biceps is counterclockwise; thus, the second condition for equilibrium (net τ = 0) becomes
Note that sin θ = 1 for all forces, since θ = 90º for all forces. This equation can easily be solved for FB in terms of known quantities,yielding. Entering the known values gives
Now, the combined weight of the arm and its load is known, so that the ratio of the force exerted by the biceps to the total weight is
This means that the biceps muscle is exerting a force 7.38 times the weight supported.
Reference : OpenStax College,College Physics. OpenStax College. 21 June 2012.
Creative Commons License : http://creativecommons.org/licenses/by/3.0/
A physical dipole consists of two equal and opposite point charges. When placed in an magnetic field, equal but opposite forces arise on each side of the ... more
Contact mechanics is the study of the deformation of solids that touch each other at one or more points. When two solid surfaces are brought into close ... more
A physical dipole consists of two equal and opposite point charges An electric dipole is a separation of positive and negative charges.The direction of an ... more
A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. The ... more
...can't find what you're looking for?Create a new formula
Calculate the force the biceps muscle must exert to hold the forearm and its load as shown in the figure below, and compare this force with the weight of the forearm plus its load. You may take the data in the figure to be accurate to three significant figures.